1. Field of the Invention
The present invention relates in general to automotive air conditioning devices, and more particularly to the automotive air conditioning devices of a type which has a plurality of doors (or dampers) for providing a plurality of air conditioning modes.
2. Description of the Prior Art
In order to clarify the task of the present invention, some conventional automotive air conditioning devices will be briefly described.
One of them is shown in Laid-open Japanese Utility Model Application (Jikkai) 63-152708. The device of the publication has an air mix door and a temperature difference compensating door. That is, the known device comprises a case having an air flow passage including an upstream part and first and second downstream parts which are branched from the upstream parts. The first and second downstream parts extend to an air mix chamber. An evaporator is installed in the upstream part of the air flow passage to cool air passing therethrough and a heater core is installed in the first downstream part of the air flow passage to heat air passing therethrough. A bypass passage extends from a part of the second downstream part to a downstream portion of the air mix chamber. An air mix door is pivotally installed in the air flow passage at the entrance portions of the first and second downstream parts and a temperature difference compensating door is installed in the bypass passage. The air mix door is pivotal between a hot air flowing position where the door opens the first downstream part while closing the second downstream part and a cool air flowing position where the door opens the second downstream part while closing the first downstream part of the air flow passage. The temperature difference compensating door selectively closes and opens the bypass passage. The bypass passage is provided at a position downstream of the temperature difference compensating door with both a ventilation opening and a defroster opening. These openings are provided with respective open/close doors (viz., ventilation door and defroster door). A foot opening is exposed to the air mix chamber, which is provided with an open/close door (viz., foot door). The ventilation opening is used for letting out the conditioned air toward a major or center part of the vehicle cabin, and the defroster opening is used for letting out the conditioned air toward .ang. windshield of the vehicle. The foot opening is used for letting out the conditioned air toward a lower portion of the vehicle cabin.
Based on the parts-arrangement of the above-mentioned conventional air conditioning device, the following two air conditioning devices "A" and "B" have been hitherto proposed, one "A" being a device which has the temperature difference compensating door linked to the air mix door, and the other "B" being a device which has the temperature difference compensating door linked to the ventilation door, the defroster door and the foot door.
The following tables "Table-1" and "Table-2" show various conditions (or positions) of the temperature difference compensating doors employed in the above-mentioned devices "A" and "B" respectively.
TABLE 1 ______________________________________ Device-A VENT B/L HEAT H/D DEF ______________________________________ M/COOL O O O O O 1/2 HOT C C C C C M/HOT 20.degree. 0 20.degree. O 20.degree. O 20.degree. O 20.degree. O ______________________________________
TABLE 2 ______________________________________ Device-B VENT B/L HEAT H/D DEF ______________________________________ M/COOL O 5.degree. O C C 20.degree. O 1/2 HOT O 5.degree. O C C 20.degree. O M/HOT O 5.degree. O C C 20.degree. O ______________________________________
In the tables, "VENT", "B/L", "HEAT", "H/D" and "DEF" represent ventilation, bi-level, heat, heat/defrost and defrost modes respectively. "M/COOL" represents a maximum cool condition provided when the air mix door opens the second downstream part of the air flow passage while closing the first downstream part of the air flow passage. "1/2 HOT" represents a half-hot condition provided when the air mix door halfly or partially opens both the first and second downstream parts of the air flow passage. "M/HOT" represents a maximum hot condition provided when the air mix door opens the first downstream part of the air flow passage while closing the second downstream part of the air flow passage. "O" represents a condition wherein the temperature difference compensating door fully opens the bypass passage, "C" represents a condition wherein the temperature difference compensating door fully closes the bypass passage and "5.degree. O" or "20.degree. " represents a condition wherein the temperature difference compensating door partially opens the bypass passage, that is, by an angle of about 5 degrees or 20 degrees.
As is seen from Table-1, in the device "A", in the half-hot condition "1/2 HOT", the temperature difference compensating door assumes its close position (viz., closes the bypass passage) irrespective of the mode taken by the device. Thus, in each mode of the half-hot condition, the warmed air passing through the first downstream part of the air flow passage and the cooled air passing through the second downstream part of the air flow passage are mixed in the air mix chamber. This means that, in the ventilation mode of the half-hot condition "1/2 HOT", temperature-controlled air can be led into the vehicle cabin from the ventilation opening. However, due to its inherent construction, in the bi-level mode of the half-hot condition "1/2 HOT", it has been difficult to provide an appropriate temperature difference between the temperature-controlled air blown from the ventilation opening and the temperature-controlled air blown from the foot opening. That is, in such mode, a desirable air conditioning wherein the passenger's heads are suitably cooled and the passenger's feet are suitably warmed is not obtained.
As is seen from Table-2, in the device "B", in the ventilation mode "VENT", the temperature difference compensating door takes its open position (viz., opens the bypass passage) throughout the "M/COOL", "1/2 HOT" and "M/HOT" conditions. That is, the temperature difference compensating door takes the open position irrespective of the position of the air mix door. This means that, in the ventilation mode of the maximum cool condition "M/COOL", the air flow resistance exhibited by the temperature difference compensating door is low and thus satisfied amount of air is blown into the vehicle cabin from the ventilation opening. Thus, in hot season like summer, a larger amount of cooled air can be led into the vehicle cabin from the ventilation opening, which makes the passengers comfortable. However, due to its inherent construction, in the ventilation mode of the half-hot condition "1/2 HOT", mixing of cooled air and warmed air is not effectively carried out before being blown into the vehicle cabin. This is because part of the cooled air passing through the second downstream part of the air flow passage bypasses the air mix chamber.